Probiotic supplementation improves quality of life and modulates oestradiol in women with endometriosis: a randomised double-blind pilot trial

Endometriosis is a chronic, oestrogen-dependent inflammatory disorder affecting up to 10% of reproductive-age women, associated with pelvic pain, infertility, and reduced quality of life. Emerging evidence implicates the vaginal microbiome and oestrogen metabolism in its pathogenesis. This study aimed to evaluate the potential therapeutic role of the oral administration of Ligilactobacillus salivarius CECT 30632, a probiotic with demonstrated ability to metabolise oestrogens in vitro, to improve the quality of life in women with endometriosis. We conducted a pilot, randomised, double-blind, placebo-controlled clinical trial assessing its effects, alongside standard dienogest treatment, in 37 women with endometriosis. Outcomes included changes in the vaginal microbiota composition (16S rRNA sequencing), in the immunological markers, in serum oestradiol levels, and in the quality-of-life of participants assessed with the EHP-30 questionnaire. Vaginal microbial diversity remained unchanged between groups; however, ∼20% of participants exhibited individualised microbiota shifts, including transitions to Lactobacillus-dominated profiles. In the immunological markers, the IL-10 levels decreased in 65% of probiotic supplemented participants (p = 0.042). Serum oestradiol levels were significantly reduced (∼50%) in the probiotic group (p = 0.013). The probiotic supplementation was associated with significant improvements in pain, emotional well-being, and perceived self-control (p < 0.05). Daily oral intake of L. salivarius CECT 30632 was associated with changes in circulating oestradiol levels and improvements in the quality of life in women with endometriosis. These preliminary findings support further powered trials to confirm efficacy and clarify underlying mechanisms. This randomised double-blind pilot trial shows that a daily oral intake of a probiotic strain reduced oestradiol levels, improved pain, emotional well-being, and overall quality of life in women with endometriosis under dienogest treatment.